Method of making a conductive vitreous seal



Filed Oct. 25, 1956 FIGA FIG.3

INVENTOR JOHANNES CORNELIS FIG.2A H62 7 JANSSEN Y AQEIZ United States Patent ice 2,964,881

METHOD OF MAKING ACONDUCTIVE VITREOUS SEAL johaunes Cornelis Janssen, 'Eindhoven, Netherlands, :as-

Filed Oct. 25, I956, Ser. N0.'-618,303 "Claims priority, application Netherlands Nov.-3, 1955 2 Claims. CI. 49-82 This invention relates to a method of sealing together glass, ceramic, or metal parts, suchas parts making up the envelope of a cathode-ray tube. It relates in particular to a method for forming'such seals with conductive links across the seal area to connect together condudtive layers or surfaces of the partsithus joined. It is frequently desirable in manufacturing envelopes for cathode-ray tubes to form the envelope in several sections, one being a funnel-shaped section made of either metal or vglass and another being a more'or less concave glass faceplate sealed to the open end of the funnel. It is customary, if the funnel section is made out of glass, to provide a conductive. coatingon its inner surface, and it is growing increasingly "common in the cathode-ray tube industry to provide a conductive layer across the inside surface 'of the glass faceplate and to connect this layer electrically to the conductive coating on the inside of the funnel or to the funnel itself, if that element bemade out of metal.

The primary object of the invention is to provide a sealing method using powered vitreous materiaL-such as glaze or enamel, which has a" relatively low meltingpoint to seal glass, 'metal,or ceramic'parts together and simultaneously to produce aconductive connection across the seal-so as to permit conductive surfaces on the two "elements thus joined to beconductive'ly -connected*togethe'r withoutthe necessity of additional connecting links.

1 Other objects will appearfrom the following specificatio'n'togetherwith the drawingin which: T i

Fig. 1 shows a cathode-ray tube constructed according to the method of the invention, parts of the cathode-ray tube being shown broken away; 7

Figs. 2 and2a show fragments of the sections of the tube in Fig. 1 immediately prior to their being joined together; and

Fig. 3 shows the sections of Fig. 2 joined together.

The invention will be described as it applies to cathoderay tubes although it will be obvious to those skilled in the art that it is equally applicable to the formation of other structures and that the example of cathode-ray tubes is chosen only to give a concrete descriptionand not to limit the scope.

In joining together the sections of an envelope of a where both sections are of glass, such as a glass funnel and a glass faceplate, each'having a conductive coating on the interior surface thereof, one or more strips of metal paste is applied to each of the sections. Each strip overlaps the conductive coatingof the section to which it is applied and extends from the conductive coating at least to the edge of the rim of the section. A layer of powdered vitreous material, also called glaze, is then laid on the rim of at least one of thesections in a layer which completely covers the entire circumference of that rim, including the part of the circumference to which the strip of metal 'paste was previously applied. Thereafter,

.the other section of the tube is brought firmly into confirst time heat is applied .to melt the vitreous material and simultaneously toheat the metal pasteand'cause the metal paste to dilfuse into the powdered vitreous mate; rial, thereby forming a conductive bridge across the s'eal in order to joint the two conductive coats of the two sections together. Care must, of course, be taken to align the strip of metallic .paste on one of the sections with-the strip of metallic paste on the others'ection before the two sections are joined together.

Considering the method in greater detail reference will first be made to Fig. l which shows a complete cathode-ray tube the sections of which'have been scaled together according to the invention. Thetube comprises a glass faceplate 1 in the form of a-shallow dish the edge of which is sealed to a glass funnel 2 which in turn is sealed to a neck 3 that contains anclectron gun (not shown). The innersurface of the faceplate 1-is covered with a layer 11 of fluorescent material which 'in turn iscovered with a layer 4'of conductive material such as aluminium. The inner surface of the conical section 2 is covered with a conductive layer 5 such as graphite.

Bridging the region in which the faceplate 1 and the conical sections 2 are sealed together are several conductive strips each consisting of a'portion 6, which is formed on the conical sections 2 and overlaps the conductive coating 5, and a portion 8, which is formed on'the faceplate section 1 and overlaps the conductive cathode-ray tube in accordance with the invention and,

tact the powdered "vitreous material and for the coating 4.

the tube.

The fabrication of the tube in Fig. -l will be described with reference to Figs. Zand 3 of which shows a cross section of a small fragment of the faceplate 1 and the cone 2. In Fig. 2 it will be seen that neither the conductive coating 4 on the faceplate' section 1 nor' order that there be a continuous conductive surface from the conical wall to'the innersurface of tlie faceplate. is applied to the cone section 2 extending from the conductive coating 5 up to the edge 13 of the rim 14 and across the rim and down on the outside to a contact member 7 which adheres firmly to the outer wall of the cone section 2and serves as a receptacle for a high voltage connection after the tube is completed. A similar strip 8 is applied to the faceplate section 1 and extends from the conductive layer 4 down to and across the rim 15. The strips 6 and S are formed of metallic paste such as silver paste or paste made up of a suspension of gold or platinum in a colloidal state in an appropriate suspension medium. A layer of vitreous material or glaze 9 which consists of a suspension of' glaze power in a liquid such as water is then placed on the rim of one of the sections, in this case the cone section 2. This glaze, which'is the sealing material, extends completely around the circumference of the cone and is laid right on top of each of the strips 6 of metallic paste.

Thereafter faceplate section 1 and the cone 2 are brought together under pressure and the sea]. area is heated to cause the glaze 9 to melt and adhere firmly to the rims of both the faceplate 1 and thecone 2 as shown in Fig. 3. At the same time the metallic particles in the strips- 6 and 8 diffuse or dissolve locally into the glaze.' That is, the metallic particles do not driftto any great distance from the strip area in which they are originally placed, although they do drift sufficiently through the contiguous portion of the glaze so Patented Dec. 20, 1960 One of these conductive strips extendsthrough the seal 'tothe outside of the tube and is connected to a contact member .7 "on the outer wall of" For this ,purpose .a "small strip 6 of metal paste l that a complete conductive bridge is formed across the glaze from the strip 6 to the strip 8 and, in particular strips shown in Figs. 2 and 3, through the sealed wall in the region 10 to that portion of the strip which conmeets with the contact member 7. If it is desired, as will usually be the case for all except one of the conductive strips, that the conductive bridge not pass through the wall of the tube to the outside thereof but simply extend across the seal on the inside of the tube it is only necessary to cover the inner surfaces of faceplate 1- and cone 2 to the edge of their rims with the strips 8 and 6, respectively as shown in Fig. 2a, and not to extend the strips 6 and 8 across to the outside edges of the rims as is shown in Figs 2 and 3. By thus restricting the strips 6 and 8, the conductive bridge will not extend through the outer surface of the tube and it will therefore be possible to cover the outer surface of the tube, even in the seal area, with the usual conductive coating which together with the conductive coating 4 and 5 forms a filter capacitor for the high voltage supply connected to the contact member 7.

In the event that one of the sections, for example, the cone 2, is made out of metal it is unnecessary to paint a conductive strip 6 upon it and it is enough merely to provide a single conductive strip 8, the metallic particles of which will migrate through the sealing enamel 9 and make contact with the metal cone. The difference between glaze and enamel is primarily a matter of terminology. Glaze is the name given to powdered vitreous 'material having a coefficient of expansion matched to that of glass, while enamel is the" name given to substantially the same material havinga coefficient of expansion matched to metal. It is, of course, well known that glass, ceramic, or metal parts sealed to one another must have substantially the same coefficient of expansion in order to prevent cracking of the seal.

-The invention is not to be considered limited to any of the particular materials or structures used as illustrations but only by the following claims.

- What is claimed is:

1. A method of sealing the rims of two vitreous members together to form a unitary structure, each of said members having a conductive layer on the same side of said structure, said method comprising steps of painting a strip of paste containing finely-divided metal in a suspension on said side of each of said members, each of said strips being sufficiently long to extend at least from an edge of the conductive layer on the respective member to an edge of the rim thereof; placing a layer of a suspension of powdered vitreous material on the rim of one of said members; pressing said rim together with said strips opposite each other to compress said vitreous material; and heating said vitreous material and said strips for the first time to cause said vitreous material to seal said members together and simultaneously to decompose the paste and release metal particles from said strips which diffuse into the contiguous portion of said vitreous material to form a conductive bridge across said vitreous material between the conductive surface of one of said members and the conductive surface of the other of said members.

2. A method of sealing the rims of two members together to form a unitary structure, at least one of said members being composed of vitreous material and having a conductive surface portion on one side thereof,

the other member being conductive, said method comprising the steps of coating a portion of said side with a paste containing finely-divided metal in a suspension to form a strip overlapping and making contact with the conductive surface thereon and extending at least to an edge of the rim of said member; covering the entire rim of one of said members with a suspension of powdered vitreous material; pressing said rims together to compress said powdered vitreous material; and heating said strip and said vitreous material to seal said members together and simultaneously to decompose the paste and release metal particles therefrom which diffuse into the contiguous portion of said vitreous material between said conductive surface and the other member.

References Cited in the file of this patent UNITED STATES PATENTS 485,478 Pollard Nov. 1, 1892 2,198,769 Goodale Apr. 30, 1940 2,321,840 McDougal June 15, 1943 2,508,001 Swedlund May 16, 1950 2,562,163 Hiensch et al. July 31, 1951 2,670,572 Smith Mar. 2, 1954 2,768,475 Seelen et al. Oct. 30, 1956 2,808,448 Bleuze et a1, Oct. 1, 1957 v UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No; 2,964,881 December 20, 1960 v Johannes Cornelis Janssen I ppears in the above numbered pat- It is hereby certified that error a id Letters Patent should read as ent requiring correction and that the sa corrected below'.

Column l line 35, for "powered" read powdered column 2, line 33, after "Figs. 2 and 3" insert each line 57, for "power" read powder o Signed and sealed this 20th day of June 1961 (SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Commissioner of Patents Attesting Officer 

